Note: Descriptions are shown in the official language in which they were submitted.
,
A nozzle for guiding a metal melt
Description
The present invention relates to a nozzle for guiding a metal melt from a
first to a second means, in particular it relates to a submerged entry
nozzle for guiding a stream of a metal melt (steel melt) from a
metallurgical melting vessel (like a tundish) into a mould (like an ingot),
both of which may also be called "reservoir".
Such a submerged entry nozzle (hereinafter called also SEN) is used in
the continuous casting of steel slabs. A SEN typically comprises a
refractory ceramic tube-like body with an inlet opening at its first end
(the upper end in its mounting position) and a conduit (an internal
channel), running from said inlet opening through said ceramic tube in
an axial direction of the nozzle (tube) to its second end (the lower end in
its mounting position), which second end provides a body stop of the
channel in its longitudinal extension and at least two lateral outlet
openings of said channel through which the metal melt enters into the
mould.
In other words: The molten metal stream, coming from a tundish or
similar vessel, enters the inlet opening, further runs vertically and
downwardly through said conduit (through the intermediate or middle
portion of the nozzle between upper and lower end) from said inlet
opening towards said outlet opening(s),
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being deflected on its way to said outlet opening(s) and leaves the nozzle
more or less perpendicular to its axial extension through these outlet
openings before entering the associated mould.
This is true as well with respect to the SEN as disclosed in WO
2007/138260 A2 with the proviso that flow dividers, arranged at the
lower (outlet) end of the nozzle, are responsible for dividing the metal
stream in numerous partial streams before leaving the nozzle.
This general design concept is further realized by EP 0946321 BI, the
nozzle of which being provided with a 2 part flow divider in its exit zone
(=lower end of nozzle) to minimize the appearance of cracks.
The known design may lead to turbulences in the metal bath in the
associated mould and/or to turbulences in any slag layer and/or any mould
(masking) powder on top of the metal bath. These effects can reduce the
steel quality and the quality of the cast product respectively. The know
design is also responsible for a limited flow capacity (flow rate).
It is an object of selected embodiments to provide a nozzle of the type
mentioned which provides a high flow-rate without causing undesired
lateral turbulences by the metal stream leaving the nozzle and entering
into the metal bath in the associated aggregate (for example a mould).
Certain exemplary embodiments provide a nozzle for guiding a metal melt
from a first apparatus to a second apparatus, comprising: a) a refractory,
tube-like body, wherein the body includes: an inlet opening at a first end
of the body; a single outlet opening at a second end of the body; and a
conduit, wherein the conduit is elongated along a central longitudinal
axis which is oriented vertically during use, wherein the conduit is
defined by an inner wall of the refractory, tube-like body and extends
from the inlet opening to the outlet opening; and b) a plurality of
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baffles, wherein the baffles project from the inner wall into the conduit,
wherein the conduit and the baffles have a geometry such that a flow
passage around the central longitudinal axis is provided for the metal
melt continuously between the inlet opening and the outlet opening,
wherein at least two pairs of baffles protrude from opposing sections of
the inner wall of the refractory body and a passage extends between the
at least two pairs of baffles through which the central longitudinal axis
extends, wherein in a front view each pair of baffles forms an inverted V
shape.
Selected embodiments are based on various technical aspects. The
probably most important is to design the nozzle such that a central
stream of metal melt may flow through the nozzle from the inlet opening
to the outlet opening in a substantially continuous axial direction. In
other words: The nozzle design allows at least part of the metal stream to
flow through the nozzle without being deflected, bypassed, turned or the
like. This central stream follows the longitudinal axial direction of the
tube-like refractory body with its inner conduit all over the nozzle
length.
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Typically this central stream is coaxial to the central longitudinal axis of
the nozzle, being an axis in a substantially vertical orientation during
use of the nozzle.
This central stream of metal melt allows a remarkable increase of the
flow-capacity of the nozzle. As this central melt stream follows a
substantially vertical, downwardly oriented direction turbulences around
the lower nozzle section and/or around the corresponding outlet section
are avoided as far as possible.
Besides this important design feature the nozzle is characterized by at
least two baffles, projecting from the inner wall of the refractory body
(being the circumferential wall of the conduit). From the aforesaid it
become apparent that the said baffles do not extend across the full width/
diameter of the conduit but that these baffles are designed and arranged
in such a way as to leave free a space between them so that the central
metal melt stream may pass therethrough along the middle section of the
nozzle between inlet and outlet openings.
Nevertheless the baffles mentioned are modifying the relevant cross-
section of the conduit and/or provide means to deflect the remaining
metal stream on its way to the lower end and the outlet openings of the
nozzle. Insofar the one metal stream entering the nozzle via said inlet
opening may be divided by these baffles into several partial streams.
Contrary to prior art nozzles as mentioned above all these partial streams
are fluidly connected with each other and/or the central stream. In other
words: The partial streams (side streams) and the central metal melt
stream are arranged in one common space defined by the circumferential
wall of the conduit and the baffles respectively.
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One embodiment is directed to a nozzle for guiding a metal melt from a
first to a second means, comprising
= a refractory, tube-like body with
= an inlet opening at its first end
= an outlet opening at its second end
= a conduit, elongate along a central longitudinal axis, which is
oriented vertically during use, limited by an inner wall of the
refractory, tube-like body and extending from said inlet opening
to said outlet opening, and
= baffles, projecting from said inner wall into the conduit, wherein
= the geometry of the conduit and the baffles is such that a
continuous flow passage (area) around the central longitudinal
axis being provided for the metal melt between the inlet opening
and one single outlet opening.
The technical and functional features mentioned are true as well with
respect to an embodiment wherein the tube like body comprises:
= adjacent to the inlet opening: an upper section of substantially
circular cross-section,
= adjacent to the outlet opening: a lower section, flared outwardly
in one first plane and flattened in a second plane substantially
perpendicular to the first plane,
= a middle section between said upper section and said lower
section, wherein the middle section provides a design transition
from the circular design of the upper section to the flattened
design of the lower section.
While the general circular outer design at the upper and a flattened
design at the lower end correspond widely
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with that of the nozzle known from WO 2007/138260 A2 the decisive
difference between both designs is that the new nozzle provides said
central axial flow stream along the whole length of the nozzle and thus
for a considerable volume of the metal melt to pass the nozzle without
any deflections. In other words: The continuous free central interspace
(extending between inlet and outlet opening of the nozzle) enables to cut
the nozzle along a plane in the longitudinal direction of the nozzle into
two pieces, for example two mirror inverted pieces, without contacting
and/or cutting any baffle.
According to one embodiment the central axial stream may extend over
the full length of the lower nozzle opening while the baffles mentioned
are responsible for at least 2 auxiliary metal streams, one on each side of
the central stream, which baffles have the function of guiding means for
directing the respective metal stream to the respective lateral section of
the one outlet opening.
These laterally escaping metal streams are of lower velocity compared
with those according to prior art nozzles and thus are causing less
turbulences in the metal bath, any slag layer and/or masking powder in
and onto the metal bath in the corresponding vessel.
Compared with the nozzle of EP0946321B1 the main differences of the
new design are: baffles are arranged in the middle section of the nozzle
between upper and lower end, they may further extend into lower and/or
upper end, always providing a free space between them for the free axial
flow of the melt. The baffles may extend >50%, >60%, >70% or even
>80% of the total axial length of the nozzle.
The disclosure further provides one or more of the following
embodiments:
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= A nozzle, wherein the design transition proceeds substantially
continuously between the upper section and the lower section. In
other words: a smooth, soft changeover between the two sections
is wanted, avoiding any sharp edges, ridges, grooves etc. This is
true as well for the inner and outer design of the nozzle.
= A nozzle with at least one first pair of baffles, protruding from
opposing sections of the inner wall of the refractory body and
leaving a passage between them through which the central
longitudinal axis extends. It is not obligatory to arrange the
baffles in a mirror-inverted fashion, although this design makes
the total metal flow more homogeneous. The baffles may also be
arranged offset with respect to the axial extension of the nozzle
and/or more than 2 baffles may protrude from the inner wall of the
body at one axial position along the nozzle length.
= At least one or each baffle (ridge) may having the shape of an
inverted V (in a front view), optionally with one or more of the
following features: a flat (even planar, if wanted) main area facing
a corresponding flat main area of the other baffle, upper and/or
lower borders substantially following the design of the
corresponding section of the inner wall of the refractory body vis-
à-vis said border.
= Based on the generic design of a nozzle like an SEN it derives
from an arrangement of the baffles according to an inverted V that
the distance between the V-legs increases toward the second end of
the nozzle, being the outlet end of the nozzle or its conduit
respectively. With a nozzle design having two lateral outlet
openings this leads to a run of the V-legs providing an angle
between 15 and 45 between a first imaginary line intersecting the
two vertical extremities of one leg and a second imaginary line
parallel to the longitudinal axis of the nozzle and intersecting the
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first imaginary line (as shown in the accompanying drawing). The
maximum angle may be set as well at 30 or 25 or 22 . This may
be realized in an analogous manner with discrete baffle bars.
= A second and/or third pair of baffles may be provided, each of
substantially same general design as the first pair of baffles, but
arranged at a distance to said first pair of baffles.
0, According to one embodiment the distance between opposing
baffles of each pair of baffles is constant or decreases toward the
outlet opening of the nozzle.
= A nozzle as mentioned with at least one first pair of baffles being
arranged, at least partially, in the lower section of the nozzle
and/or
= A nozzle with at least one first pair of baffles being arranged, at
least partially, in the middle section of the nozzle.
= At least one baffle or a first pair of baffles may terminate in the
outlet opening, although it is possible as well to arrange the
= baffle(s) in such a way that it/they end(s) at a distance before the
corresponding outlet section of the outlet opening.
= The nozzle may have at least one of the following dimensions:
= a distance between opposed baffles of between 5 and 15mm
O a baffle height, perpendicular to the central longitudinal
axis (A) of 5-20mm
= an inlet opening with an inner diameter of between 40 and
120mm
= an outlet opening with a length of between 100 and 400mm
and a width of between 5 and 40mm.
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= an outlet opening with a length of at least twice the diameter
of the inlet opening and/or a width of at most half the
diameter of the inlet opening. This corresponds to a general
design of a so called thin-slab SEN (german: "Breitmaul
ETA")
= the outlet opening is defined by a central axial outlet section
and two lateral outlet sections, extending towards the inlet
opening.
Referring to the "inverted V" design of a baffle one further embodiment
provides for a "V with curved legs". This curvature may be parallel to a
corresponding curvature of the inner wall of the refractory body (i.e. the
curvature of the conduit wall). Another embodiment provides a design
according to which any distance between the conduit wall and the
corresponding border surface of the baffle becomes smaller in the
direction towards the outlet opening.
The nozzle can be made of any conventional refractory material (like a
material based on MgO, Al2O3, ZrO2, C) and may be manufactured by
any conventional process (i.a. isostatic pressing).
Unless otherwise disclosed the term "substantially" characterizes the
corresponding feature as achieved under technical aspects. For example:
"Substantially vertical orientation of the nozzle during use" does not
necessarily mean an exact vertical orientation under mathematic aspects
but the typical technical position.
The drawing shows, in a highly schematic way, in
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Fig. la and 1 b: three-dimensional views onto a nozzle according to the
invention, partly cut off
Fig. 2: a three-dimensional view onto the inner contour of the nozzle
according to Fig. la and lb
Fig. 3: an outflow area of the nozzle and corresponding flow directions
of the melt.
All Figures show a so-called submerged entry nozzle (SEN), made of an
MgO based batch, isostatically pressed and fired according to
conventional techniques.
The SEN shows a tube-like refractory body 10 with one single inlet
opening 12 of substantially circular cross section at its first end (the
upper end in the use position as shown) and one single outlet opening 14
of substantially rectangular/oval cross section at its second end (the
lower end in the use position). Inlet opening 12 and outlet opening 14
are bridged by a conduit 16, elongate along a central longitudinal axis
(A) of the body 10, which axis is oriented substantially vertical during
use of the nozzle. Conduit 16 is defined by an inner wall 10i of the
refractory tube-like body 10.
Corresponding to the general design of upper and lower section 18,20,
inlet opening 12 and outlet opening 14 of said nozzle, conduit 16 varies
its cross section from circular to a geometry similar a flat oval or a thin
rectangle with rounded end portions. This change is mostly realized in
the middle section 22 (Fig. 2).
The general design may be described as follows: tube like body 10
comprises, adjacent to the inlet opening 12, an upper section 18 of
substantially circular cross-section, adjacent to the outlet opening 14, a
lower section 20, flared outwardly in one first plane (the drawing plane)
and flattened in a second plane (vertical to the drawing plane),
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substantially perpendicular to the first plane, a middle section 22
between said upper section 18 and said lower section 20, wherein the
middle section 22 provides a design transition from the circular design
of the upper section 18 to the flattened design of the lower section 20.
This design transition proceeds substantially continuously between upper
and lower section 18,20, as may be seem from Figures la, lb and 2.
The lower section 20 therefore has a length about 8 times its width. The
same being true for the cross section of the corresponding outlet opening
14.
From each of opposing sections of the inner wall 10i in the middle
section 22 and the lower section 20 baffles 30, 32, 34, 36 protrude into
the conduit 16, thereby forming a gap 38 between corresponding flat
main areas (front surfaces) 30f, 32f, 34f, 36f. Baffles 30,32 and 34,36
respectively are linked together, thus each providing the shape of an
inverted V with slightly curved outer borders 30b, 32b, 34b, 36b and
inner borders. These borders follow the corresponding shape of the inner
wall 10i opposite the respective border.
The two pairs of baffles 30,32; 34,36 on each side of the conduit 16 (Fig.
2 only shows one side) are arranged offset along the central longitudinal
axis A of the nozzle and ending in the corresponding common outlet
opening 14.
The angle a between the central longitudinal axis A and a line
intersecting the two vertical extremities of one baffle 32 is about 17 (a
typical range being 15 -25 ), i.e. the V includes an angle of 2 x 17 =34 .
This is true as well with respect to the lower baffles 34,36.
Because of the distance (gap 38) of corresponding baffles 30, 30; 32, 32;
34, 34; 36, 36 it becomes clear that the nozzle provides a central passage
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around the central longitudinal axis A which runs continuously and
substantially straight from the inlet opening 12 to the outlet opening 14.
Correspondingly the nozzle provides a central passage for the metal
melt, along which the melt is fed in a more or less linear way (arrow D
in Fig. 3) to and through the outlet opening 14 and thus in a downwardly
oriented vertical orientation into a corresponding mould 40 (Fig. 3).
The baffles 30, 32, 34, 36, arranged adjacent on both sides of the central
passage, cause the melt to follow their respective borderline and thus
being directed to lateral sections 141 of the common outlet opening 14
and leaving the outlet opening 14 substantially laterally (arrows L in
Fig. 3).
It is important to strengthen that although the metal stream takes
different directions while leaving the nozzle there is only one outlet
opening 14 and all these central and lateral metal streams are in fluidic
contact with each other.
Fig. 3 shows three main directions of the outflowing metal stream. One,
the central stream D, in extension of axis A vertically downwardly and
the other two laterally (L) at opposing sides of the outlet opening 14.
By this design the flow through rate may be increased and turbulences in
the metal bath of the associated vessel (mould 40) are reduced.
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